Wave-signal receiver arrangement



Feb. 4, 1947. H, A, WHEELER WAVE-SIGNAL RECEIVER ARRANGEMENT Filed Aug. 15, 1944 INVENToR l HAROLD A. WHEELER BY Patented Feb. 4, 1947 UNITED STATES PATENT oFFicfE WAVE-SIGNAL RECEIVER ARRANGEMENT Harold A. Wheeler, Great Neck, N. Y., assigner, by mesne assignments, to Hazeltne Research, Inc., Chicago, Ill., a corporation of Illinois Application August 15, 1944, Serial No. 549,504

(Cl. Z50- 13) 16 Claims. 1

This invention relates, in general, to a wavesignal receiver arrangement and is particularly directed to a receiver arrangement for operation at a, predetermined frequency to translate received wave signals and which is adapted to share a common antenna system with an arrangement for transmitting wave signals of a frequency which corresponds substantially to the operating frequency of the receiver, as in a radio-locator or direction-finder system.

For optimum operation, a radio-locator or direction-iinder system of the type under consideration should satisfy the following requirements: (a) the receiver should be characterized by a high signal-to-noise ratio; (b) during intervals ci wave-signal reception, the receiver should present an input-terminal impedance approximately equal to that of the antenna system, while the transmitter should present ,a widely different output-terminal impedance; and (c) during intervals of wave-signal transmission, the outputterminal impedance of the transmitter should approximate the terminal impedance of the antenna system, but the input impedance of the receiver should be widely diierent therefrom. Preferably, during alternate intervals of reception and transmission, the transmitter and receiver should alternately exhibit the properties of a, wave-signal reflector, that is, present a very high or innite impedance at their respective junctions with the common antenna system. 'Where these operating conditions are fulfilled, the system exhibits its greatest sensitivity and the receiver and transmitter have a minimum interaction or loading effect on one another, permitting maximum useful energy transfer to the receiver and from the transmitter during periods of reception and transmission, respectively.

Prior art systems are known which are designed to realize the above-recited optimum conditions. In one such system the receiver arrangement has an input impedance, during normal wave-signal reception, which substantially equals thatof the antenna system and is coupled to the antenna system by means of a, transmission-line section which establishes proper impedance matching therebetween. 'Ihe initial stage of the receiver comprises a grid-driven radio-frequency amplier which, during intervals of wave-signal transmission, peak-rectiiies the transmitted signal in its grid circuit, establishing a bias potential to bias the rst stage substantially to anode current cutoff. In this manner, the input impedance of the receiver is inodied to lessen the load provided by the receiver on the transmitting arrangement during intervals of transmission. While such an arrangement is generally satisfactory, it employs a screen-grid tube in the radio-frequency amplifier in order that the system may operate over a wide frequency range. As is well underu stood, a screen-grid tube does not provide a maximum signal-to-noise ratio and, for certain instaliations, may constitute an undesirable operating limitation of the described system.

In other prior art systems the initial stage of the receiver includes a cathode-driven triode amplier which affords a desirable signal-tonoise ratio. However, in these other systems the input-terminal impedance of the receiver is not modified as required substantially to lessen the loading eect of the receiver on the transmitter during intervals of wave-signal transmission. This results from the fact that the transmitted signal is applied to the cathode of the rst receiver stage so that during intervals when the transmitted signal could otherwise be peak-rectied to bias the amplier to anode current cutoi, as in the above-mentioned prior art systems, the peak value of the signal input to the receiver exists between the anode and cathodeelectrodes of the lirst amplier of the receiver, rendering the amplifier highly conductive. This produces an input-terminal impedance closely approaching that presented during periods of normal reception. As a consequence, the receiver constitutes a substantial load on the transmitter and undesirably decreases the power of the transmitted signal radiated by the common antenna system.

It is an object of the invention, therefore, to provide a wave-signal receiver arrangement which avoids one or more of the above-mentioned limitations of prior art arrangements.

It is another object of the invention to provide an improved wave-signal receiver arrangement for operation at a predetermined frequency to translate received wave signals and adapted to share a common antenna system with an arrangement for transmitting wave signals of a frequency which corresponds substantially to the operating frequency of the receiver.

It is a specic object of the invention to provide an improved wave-signal receiver arrangement adapted to share a common antenna system with a transmitting arrangement operating at substantially the same frequency, but which provides a minimum load on the transmitter during intervals of wave-signal transmission.

In accordance with the invention, a wave-signal receiver arrangement for operation at a predetermined frequency to translate received wave signals and adapted to share a common antenna system with an arrangement for transmitting wave signals of va frequency which corresponds substantially to the operating frequency of the receiver comprises a signal-translating channel. The signal-translating channel has an input circuit which presents a predetermined terminal impedance to the antenna system during operating intervals oi normal wave-signal reception and which tends to provide a substantial load on the transmitting arrangement during operating intervals of wave-signal transmission, The receiver arrangement also comprises means including a rectifier device exclusive of the signal-translating channel and responsive to the transmitted signals for deriving a control effect and means for utilizing the control effect so to Vary the terminal impedance of the input circuit or the signaltranslating channel as substantially to lessen the load provided thereby on the transmitting arrangement during operating intervals of wavesignal transmission.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope Will be pointed out in the appended claims.

ln the drawing, Fig. 1 represents a complete radio-locator system, including a Wave-signal receiver arrangement in accordance With the invention;and Fig. 2 comprises graphs utilized in explaining the operation thereof.

Referring now more particularly to Fig, l, the radio-locator system there represented includes an antenna system l, l l which is common to and adapted to be shared by receiver and transmitter arrangements, described more particularly hereinafter. For convenience of illustration, the antenna system is shown as a simple dipole, a1- though other systems having more sharply directive radiation characteristics may be utilized, ii desired. Also, suitable arrangements may be provided ior effectively rotating the antenna directive pattern for scanning purposes. The specific properties of the antenna system are dictated by the operational requirements of the composite locator system and may vary with particular installations. A coaxial transmission line I2 connects the antenna system With a junction box i3, the transmission line being selected to have a characteristic impedance substantially equal to the terminal impedance of the antenna system.

The wave-signal receiver arrangement of the radio-locator system operates at a predetermined frequency to translate received Wave signals and, as illustrated, is of the superheterodyne type. This receiver comprises a signal-translating channel for translating received signals and has a pair of input terminals 2B, 2l. The channel includes a radio-frequency ampliiier 22, presently to be described, to which are coupled in cascade an oscillator-modulator 23, an intermediate-frequency amplifier 23 of one or more stages, a detector Z for deriving the modulation components of received wave signals, and an amplier 26 of one or more Stages. The output circuit of amplier is coupled to output terminals 2, 28 to which a suitable utilizing circuit, not shown, may be connected.

Radio-frequency amplier 22 is represented as consisting of a single stage, but it Will be understood that as many stages of amplification may be employed as desired. This amplier comprises a cathode-driven electron-discharge means, specirlcally a cathode-driven triode amplifier provided by one section of a duo-triode 3i! having a cathode element 3l common to both sections thereof. The control electrode and anode elements of the amplifier section are indicated by reference numerals 32 and 33, respectively. The input circuit of the amplifying section of tube constitutes the input circuit of the described signal-translating channel. This input circuit comprises the primary winding 34 of a transformer 313, 35 and is rendered selective through variation of the inductance of winding Sil. The capacitance, which provides With winding 34 a resonant circuit, includes a condenser 35, the capacitance to ground of cathode element 3l, the inherent capacitance of the winding and other associated stray capacitances. This input circuit is coupled to the input terminals of the signaltranslating channel through a condenser 31. Control electrode 32 of the amplifying triode is maintained at substantially ground potential and anode electrode 33 thereof is coupled to a tuned output circuit. rihe output circuit is provided by a variable inductor 38 resonated by a condenser SS, shown in broken-line construction since it may be comprised in whole or in part of the inherent capacitance of inductor 3B and associated stray capacitances. The output circuit of the amplifier is coupled through a condenser 4U to the input circuit of oscillator-modulator 23. A suitable source of space current, indicated +B, is coupled to the anode electrode 33, while a selfbiasing circuit is coupled to cathode element 3l. The biasing circuit includes a radio-frequency choke 4l and a bias resistor 32, by-passed for radio-frequency currents 4,by means of a condenser 43. Cathode 3l is of the indirectly heated type, having a heater circuit which consists of a bilar Winding 44 coupled to a source of heater voltage, indicated A.

The operating potentials applied to the electrode elements of the amplifying section of tube 3U are such that this section is operated substantially above anode current cutoi during operating intervals of normal Wave-signal reception. Furthermore, the described input circuit thereof presents, during such operating intervals, a predetermined impedance ai; terminals 20, 2| which is approximately equal to the terminal impedance of .the antenna system l D, Il and which, for this reason, tends to provide a substantial load on the .transmitting arrangement during operating intervals of wave-signal transmission, as will be more clear hereinafter.

The receiver arrangement under consideration also comprises means including a peak-rectiiier device exclusive of the defined signal-translating channel and responsive to transmitted signals for deriving a control effect. The rectifier device is provided by the remaining section of duo-triode 30 comprising electrode elements 5S and 5l. Electrode 5l is grounded and electrode 50 serves as the anode element of the rectiiier. Since the cathode 3l is common to the amplifying and rectifying sections of tube 3i), the self-biasing arrangement of the amplifier, including resistor 42, constitutes means for deriving from the amplifying section and for applying to the rectifier device an amplitude-delay bias. Resistor 42 is selected of such value that the rectier device is unresponsive to signals received during normal intervals of Wave-signal reception. The load circuit of the rectier includes a time-constant circuit across which a unidirectional control potential, or control effect, is developed. The time-constant circuit comprises a parallel combination of a resistor 52 and a condenser 53 and is coupled to the anode element of the rectifier device through secondary Winding 35 of transformer 34, 35. The rectifier circuit is arranged to have a fast charging time constant but a slow discharge time constant. In particular, the values of elements 52 and 53 are selected to cause the discharge time constant .to be long with reference to the period corresponding to the carrier component of the transmitted signals in order that such signals may be peak-rectiiied. The described rectifier device may be considered to be exclusive of .the receiver signal-translating channel in View of the fact that normal signal translation through the receiver is independent of the rectifying section of tube 30.

The receiver arrangement also has means for utilizing the .control effect derived by the rectifier device so to vary the terminal impedance of the input circuit of amplifier 22 and the signal-translating channel as substantially to lessen the load provided .by the channel on the transmitting arrangment during operating intervals of wave-signal transmission. To this end, a conductor Etaplplies the unidirectional control potential With negative polarity to control electrode 32 ci amplier 22, biasing the amplifier in the direction of anode current cutoff,

The transmitted signals are applied to the rectierdevice With such intensity that the magnitude of this control potential is such as to bias the amplifier section of tube 3B substantially to anode current cutoff, thereby to effect a maximum impedance change at input terminals 20, 2i of the receiver during intervals of transmission. This is accomplished by applying the transmitted signals to the rectiiier device with greater intensity than such signals are applied to the cathode-driven amplifier. In this connection, it Will be seen that signals applied to input terminals 2D, 2| of the receiver are applied with a given phase and a, given intensity to cathode 3l of the amplifying section of tube Si! and, since this cathode element is common to both sections of tube 30, such signals are applied with the same phase and same intensity to the cathode circuit of the rectifier. Transformer 3G, 35 provides additional means for applying such signals to the anode element of the rectifier device, the secondary Winding 35 being poles so that this lastnamed means applies received signals to the anode element of the rectier device in phase addition with the same signals as applied directly to the cathode.

A coaxial transmission-line section GEB couples the receiver arrangement t0 antenna system lll, l l, having a junction With the antenna transmission line l2 as indicated at iii. This coupling arrangement is effective to apply both received and transmitted signals from the antenna feeder I2 to the input terminals of the receiver. Transmission-line section 55@ is selected to have a characteristic impedance corresponding to the terminal impedance of the receiver during intervals of normal wave-signal reception so that during such intervals the receiver and antenna system are coupled with matched impedances. A portion of the inner conductor of transmission line 50' has a U-shaped coniiguration telescopically adjustable within a cooperating portion 63 for the purpose of adjusting the effective electrical length of the transmission line. Through this adjustment, the eiective electrical length of line BQ is established to have such a value at the operating frequency of the transmitter that during intervals of Wave-signal transmission when the input impedance of the receiver has its modied value, transmission-line section t@ comprises an impedance transformer which transforms the receiver input impedance to a maximum value at the junction 6|.

The transmitting arrangement of the radio-locator system has substantially the same operaterably including provisions for keyed operation to transmit a pulse-modulated carrier-frequency wave signal when keyed into operation. A schematic circuit representation of a portion of the transmitter arrangement is included Within block 59, showing a preferred method for coupling the transmitter to antenna system l0, il. Tube it of the schematic circuit diagram represents a power tube of the transmitter, such as a power amplifier or oscillator having a tuned output circuit comprising an inductor il and a tuning condenser l2. Tuned circuit ll, 'E2 is selected to be a low-loss circuit and is coupled to suitable output terminals 13, Hi through an inductor l5. Inductors 'il and l5 are arranged for optimum coupling during periods of transmission when tube is conductive, but have much greater than optimum coupling during intervals of Wave-signal reception when tube 'l0 is in a quiescent or nonconductive state. The coupling is such that this final stage` of the transmitter presents, during periods of transmission, a predetermined output impedance at terminals i3, 'M which corresponds substantially to the terminal impedance of the antenna system. During periods of wave-signal reception, however, when the degree of coupling between inductors 'H and 'i5 is materially different, a much diiferent terminal impedance is presented at terminals 13, M.

Transmission-line section l@ couples the transmitter arrangement .to junction 6l of the antenna transmission line i 2. Transmission-line section l is generally similar to section 6i), having a characteristic impedance corresponding to the terminal impedance of the transmitter arrangement during intervals of normal Wave-signal transmission for coupling the antenna system thereto with matched impedance. This line also includes an adjustable section, comprising telescoping elements il and i8, for adjusting its effective electrical length. The length is so selected that at the operating frequency of the receiver line section 'F6 comprises an impedance transformer which transforms the modied terminal impedance of the transmitter obtained during intervals of normal Wave-signal reception when tube l@ is in a quiescent condition to a maximum impedance at the antenna junction 6l.

In considering the operation of the radio-locator system of Fig. l, it Will be assumed initially that the transmitter arrangement is in its quiescent condition and that the receiver arrangement is conditioned for normal wave-signal reception. For the assumed conditions, the outputterminal impedance of the transmitter is Iwidely dierent from the characteristic impedance of transmission-line section l and the transmitter has its minimum loading effect on the receiver arrangement. The receiver, on the other hand, presents its normal input impedance which corresponds both to the characteristic impedvances of transmission lines Si! and l2 and the terminal impedance of the antenna system Il), i l. Thus, the amplifying section of duo-triode Sli is substantially matched to the antenna system for maximum energy transfer therebetween. For this condition, the operating characteristic of radio-frequency amplifier 22 is represented by the full-line curve of Fig. 2, which characteristic represents the plate current-cathode voltage operating characteristic for the normal grid bias ego. VIt is to be noted that the abscissa. axis is drawnwith positivecathode:voltages;indicated to the left ofthe ordinate axis yO -iD andwithnegative cathode voltages indicatedgto the right of this ordinate axis. This unconventional ab'scissa scale has been chosen in Ordertilat; the charac-v teristic may resemble the more iamiliar plate current-grid voltage characteristic of'a triode amplifier. The self-biasing: circuit ofthe amplifier establishes an operatingr point indicated bythe broken ordinate lineV a--.b. This operating pointis such that for signals applied. to thereceiver during normal intervals of wave-signalv reception amplier 22V does not draw, grid` current- Curve e1 of Fig. 2- representsthe magnitude of normal received signals and shows the amplitude-delay biaswhich is applied tocathodel to be suchv that the rectifier device 3l, illis unresponsive to signals received duringnormaloperating intervals of Wave-signal reception. Thus, any such received Isignals are translated; through the` receiver arrangement, in accordance. with conventional superheterodyne reception, and the modulation components thereof derived in. detector 25 are amplied in amplifier 26- and applied to output terminals El, for utilization.

Assume, now, that-the transmitter E9 is keyed into operation to transmit a signal. At the instant transmission isY initiated,` the output-terminal impedance of the transmitter is modified to a value which corresponds to the characteristic impedance of transmission lines Hfand l2, thereby coupling the transmitter to the antenna with matched impedances. However, the receiver arrangement likewise presents the same impedance to antenna junction S! at the start of transmission and, hence, tends to provide a substantial load onl the transmitting arrangement. Therefore, the transmitted signal is applied with substantial intensity to the input circuit of the receiver arrangement. The magnitude of the transmitted signal applied toinput terminals 2l), 2l may be as represented by curve e2 of Fig. 2.

lleglectini-.` for a moment the eiect of secondary winding of transformer 34, 35, it-Will be apparent that the rectifier section of. tube 3l] rectifies that portion of the applied transmitted signal which excess the amplitude-delay bias existing on its cathode. That is to say, the rectiiier develops across time-constant circuit 52 53 a unidirectional control potential proportional to dimension` line di of Fig. 2. This control potential, being applied as an operating bias to control electrode S2 of amplier 22, eiectively shifts the operating characteristic of the ampliner a corresponding amo-unt, as indicated by brokenline curve egl. By projecting curve ez upon the new characteristic esl, it becomes evident that this bias is insuflicient to bias amplifier 22 to anode current cutoi, as required to effect a maximum impedance change at the input terminals of the receiver arrangement. Consequently, transformer 34, 35 is provided to apply an additional portion of thetransmitted signal to the anode element of rectilier 3l, 5t in phase addition with that applied directly to its cathode element. This additional portion of the transmitted signal is selected of such value that the resulting control potential developed by time-constant circuit 52, 53 shifts the operating characteristic of the amplifier, as indicated lby dash-dot curve egg. In other words, the control potential developed is suicient to bias amplifier 22 to anode currentcutoi and effect a maximum impedance change at input terminals 20, 2| of the receiver arrangement. Since the .rectifierdevice hasa- 81 fasticharginsiimeconstant; thezdescrbed-.chanse in input; iinpedarle.v is accomplished early in theA cycle ci the., transmitter arrangement;Y Transmissiony line lgtransforms this` new. value of the receiver; input impedance to a highvalueatxantenna junction @i so asY substantially to' lessenV the load provided by the receiver on the trans-- mitting arrangement during operating intervals of wave-signal transmission.

At thecompletion rof -the transmission cycle, the bias, potential established by time-constant' cir:- Cuit 5.2; 'decaysto zero, reestablishinginthe receiver normal,` conditions .for wave-signal reception. At the same time, sincetube llof the transmitter arrangement is returned toits quiescent state, the transmitterpresents al maximum impedance at junctionlii. Therefore, by the time the transmitted signal is reiiected'from the object. to be4 located andreturned to antenna systemlll; il, the first-described conditions are established in which the receiver is matched with the antennaand thetransniitter has rits minimum loading effect on the receiver. The. reflected signal is, therefore, translated in conventionalmanner to output terminals 2?, 28' of thereceiver foruti-v lization to obtain the required indication.

In the foregoing. descriptionit was pointed out that the receiver and transmitter arrangements` have modified terminalimpedances during intervals of transmission and reception, respectively; In each instance, the modified impedance was said to be transformed by the associated transmission-line section to a high impedance at the antenna junction-,5| in orderto lessen the loading eiect of the. receiver and transmitter upon one another during appropriate portions of the locator operating cycle. This phenomena may be viewed differently, in terms of signal reiiection. That is, the terminal impedance of. the transmittel' during normal periods or reception is such as to effect a 'substantial impedance mismatch between the` transmitter and its associated'line section i6. Preferably, the impedance mismatch should cause the transmitter to appearfto beA a perfect reiiector during periods of reception so that the entirereceived energy may be delivered to the receiver. Likewise, during intervals, of transmission thechange in impedance of the receiver` should cause the receiver to appear as a perfectreiiector, to minimize v, itsloading eiiect on the transmitter.

In oneembodiment of the invention found to havepractical utility the following circuit componentswere-utilized in the initial stage of the described receiver:

Tube 3Q; Type 6J6 Resistor i2 47 ohms Resistor 52 22,06) ohms Condensers 3E and 9---- 5 micromicrofarads Condenser 3i 4 micromicrofarads Condenser ISS micromicroiarads Condenser 53 50 micromicrofarads inductor 38;. Adjusted to tune over operating-frequency range Transformer Sli', 35 Air-core transformer;

3% turn primary and single-turn secondary B-supply -195'volts Transmission line 60 Section of 50-oh1n coaxial 1 cable Operating4 frequency 15T-187 i'negacycles V.fafiiasls The described locator system will be seen to satisfy the aforementioned operating conditions required for optimum operation. By using a cathode-driven triode amplifier in radio-frequency amplifier 22, a high signal-to-noise ratio is obtained and the receiver may be operated over a Wide range of frequencies.

While there has been described What is at present considered to be the preferred embodiment of this invention, it Will be obvious to those skilled in the art that various changes and modications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall Within the true spirit and scope of the invention.

What is claimed is:

1. A Wave-signal receiver arrangement for operation at a predetermined frequency to translate received wave signals and adapted to share a common antenna system with an arrangement for i transmitting Wave signals of a frequency Which corresponds substantially to said predetermined frequency comprising, a signal-translating channel having an input circuit which presents a predetermined terminal impedance to said antennai system during operating intervals of normal Wave-signal reception and which tends to provide a substantial load on said transmitting arrangement during operating intervals of Wave-signal transmission, means including a rectifier device exclusive of said signal-translating channel and responsive to said transmitted signals for deriving a control eiect, and means for utilizing said conm trol effect so to vary the terminal impedance of said input circuit as substantially to lessen the.'

load provided by said signal-translating channel on said transmitting arrangement during operating intervals of Wave-signal transmission.

2. A Wave-signal receiver arrangement for operation at a predetermined frequency to translate received Wave signals and adapted to share a common' antenna system with an arrangement for transmitting wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating.

channel having an input circuit which presents a predetermined terminal impedance to said antenna system during operating intervals of normal Wave-signal reception and which tends to provide a substantial load on said transmitting arrangement during operating intervals of Wavesignal transmission, means including Aa peakrectifier device exclusive of said signal-translating channel and responsive to said transmitted signals for deriving a control effect, and means for utilizing said control effect so to vary the terminal impedance of said input circuit as substantially to lessen the load provided by said signaltranslating channel on said transmitting arrangement during operating intervals of Wave-signal transmission.

3. A wave-signal receiver arrangement for operation at a predetermined frequency to translate received Wave signals and adapted to share a common antenna system With an arrangement for transmitting Wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating channel having an input circuit which presents a predetermined terminal impedance to said antenna system during operating intervals of normal Wave-signal reception and which tends to provide a substantial load on said transmitting arrangement during operating intervals of Wavesignal transmission, means includinga rectifier minal impedance of said input circuit as substantially to lessen the load provided by said signaltranslating channel on said transmitting arrangement during operating intervals of Wave-signal transmission.

4.. A wave-signal receiver arrangement for o-p eration at a predetermined frequency to translate received Wave signals and adapted to Ashare a common antenna system with an arrangement -for 'transmitting Wave signals of a frequency which corresponds substantially to said predetermined frequencf,T comprising, a signal-translating channel having an. input circuit which presents a predetermined terminal impedance t0 Isaid antenna system during operating intervals of normal wave-signal reception and which tends to provide a substantial load on said transmitting arrangement during operating intervals of Wave-signal transmission, means including a rectifier device exclusive ci said signal-translating channel and responsive to said transmitted signals for deriving a control effect, means for applying an amplitude-delay bias to said rectifier device such that said device is substantially unresponsive to said received signals, and means for utilizing said control effect so to vary the terminal impedance of said input circuit as substantially to lessen the load provided by said signal-translating channel on said transmitting arrangement during operating intervals of Wavesignal transmission.

5. A wave-signal receiver arrangement for operation at a predetermined frequency to translate received Wave 'signals and adapted to share a common antenna system With an arrangement for transmitting Wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating channel for translating said received signais, electron-discharge means included in said channel having an input circuit which presents a predetermined terminal impedance to said-antenna system during operating intervals of normal wave-signal reception and which tends to cause said channel to provide a substantial load on said transmitting arrangement during operating intervals of Wave-signal transmission, means including a rectifier device exclusiveof said signal-translating channel and responsive to said transmitted signals for deriving a control eifect, and means for utilizing said control effect so to vary the terminal impedance of said input circuit as substantially to lessen the load provided by said signal-translating channel on said transmitting arrangement during operating intervals of Wave-signal transmission.

6. A Wave-signal receiver arrangement for operation at a predetermined frequency to translate received wave signals and adapted to share a common antenna system with an arrangement for transmitting Wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating channel for translating said received signals, electron-discharge means included in said channel operated substantially above anode current cutoff during intervals of normal Wave-sig-Y 13 channel having an input circuit which presents a predetermined terminal impedance to said an- 'tenna system during operating intervals of normal Wave-signal reception and which tends to cause said channel to provide a substantial load on said transmitting arrangement during operating intervals of wave-signal transmission, means including a rectifier device exclusive of said signal-translating channel and responsive to said transmitted signalsfor deriving a unidirectional control potential, means for utilizing said control potential to bias said electron-discharge means in the direction of anode current cutoff, means for coupling said signal-translating channel to said antenna system so that said received and transmitted signals are applied thereto with a given phase and given intensities and for applying said transmitted signals to said rectiiier device with substantially the same phase and intensity, and additional means for applying said transmitted signals with a predetermined intensity to said rectifier device in phase addition with said last-named means so that the magnitude of said control potential is such as to bias said electron-discharge means to anode current cutofr and vary the terminal impedance of said input circuit so as substantially to lessen the load provided by said signal-translating channel on said transmitting arrangement during operating intervals of wave-signal transmission.

12. A Wave-signal receiver arrangement for operation at a predetermined frequency to translate received Wave signals and adapted 'to share a common antenna system with an arrangement for transmitting Wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating channel for translating said received signals, a cathode-driven electron-discharge means included in said channel operated substantially above anode current cutoff during intervals of normal wave-signal reception and having an input circuit Which presents a predetermined terminal impedance to said antenna system during such intervals but which tends to cause said chan- S- nel to provide a substantial load on said transmitting arrangement during operating intervals of Wave-signal transmission, means including a rectifier device having a cathode element in common with said electron-discharge means and efn' fectively exclusive of said signal-translating channel for responding to said transmitted signals to derive a unidirectional control potential, means for utilizing said control potential to bias said electron-discharge device in the direction of anode current cutoi, means for coupling said channel to said antenna system and for applying said received and transmitted signals with a given phase and given intensities to said common cathode element of said electron-discharge means and said rectifier device, and additional means for applying said transmitted signals with a predetermined intensity to said rectifier device in phase addition with said last-named means so that the magnitude of said control potential is such as to bias said electron-discharge means substantially to anode current cutoff and vary the terminal impedance of said input circuit so as substantially to lessen the load provided by said signal-trans lating channel on said transmitting arrangement during operating intervals of Wave-signal transmission.

13. A wave-signal receiver arrangement for operation at a predetermined frequency to translate received wave signals and adapted to share la a common antenna system With an arrangement for transmitting Wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating channel for translating said received signals, a cathode-.driven electron-discharge means included in said channel operated substantially above anode current cutoff during intervals of normal Wave-signal reception and having an input circuit which presents a predetermined terminal impedance to said antenna system during such intervals but which tends to cause said channel to provide a substantial load on said transmitting arrangement during operating intervals of wave-signal transmission, means including a rectifier device having a cathode element in common With said electron-discharge means and an anode element and being eifectively exclusive of said signal-translating channel for responding to said transmitted signals to derive a unidirectional control potential, means included in said input circuit for applying an amplitude-delay bias to said rectier device such that said device is substantially unresponsive to said received signals, means for utilizing said control potential to bias said electron-discharge means in the direction of anode current cutoff, means for coupling said channel to said antenna system and for applying said received and transmitted signals with a given phase and given intensities to said common cathode element of said electron-discharge means and said rectifier device, and additional means for applying said transmitted signals with a predetermined intensity to said anode element of `said rectifier device in phase addition with said last-named means so that the magnitude of said control potential is such as to bias said electrondischarge means to anode current cutoff and vary the terminal impedance of said input circuit so as substantially to lessen the load provided by said signal-translating channel on said transmitting 'arrangement during operating intervals of wave-signal transmission.

14. A Wave-signal receiver arrangement for operation at a predetermined frequency to translate received Wave signals and adapted to share a common antenna system With an arrangement for transmitting Wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating channel for translating said received signals, electron-discharge means included in said channel having an input circuit which presents a predetermined terminal impedance to said antenna system during operating intervals of normal Wave-signal reception and which tends to cause said channel to provide a substantial load on said transmitting arrangement during operating intervals of Wave-signal transmission, means including a rectier device exclusive of said signal-translating channel and responsive to said transmitted signals for deriving a unidirectional control potential, means for utilizing said control potential to bias said electron-discharge device in the direction of anode current cutoff, means for coupling said channel to said antenna system so that said received and transmitted signals are applied thereto with a given phase and given intensities and for applying said transmitted signals to said rectifier device with substantially the same phase and intensity, and additional means coupled to said channel for applying said transmitted signals with a predetermined intensity to said rectifier device in phase addition with said last-named means so that the magnitude of said control potential is such as to biiass'aid electron-discharge means to anode current cutoff and vary the terminal impedance ci said 'input circuit so 'as substantially to lessen the-load `providedby said signal-translating channel on said transmitting arrangement during operating 'intervals of Wave-signal transmission.

l5. v*A Wave-signal receiver arrangement for operation at a predetermined 'frequency to translate received Wave signals and adapted to share 'a 'common antenna system with an arrangement for ltransmitting wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translatingchannel having an input circuit'which nresents'a predetermined'terminal impedance to said antenna system during operating intervals ci normal wave-signal reception and which tends to 'provide a substantial load on said transmitting arrangement during operating intervals of Wavesignal transmission, means including a rectifier device exclusive 'of said signal-translating channel and responsive 'to said transmitted signals fer Ideriving a control effect, means for utilizing said control eiiect to cause said input-'circuit to 'have a modied 'terminal 'impedance during operating inter-vals of Wave-signal transmission, and an adjustable ltr'ansmission-'line section having 'a characteristic impedance corresponding to said predetermined terminal impedance for coupling said signal-translating channel to said antenna system with substantial impedance matching during intervals of 'Wave-signal lreception and having such an eiective `electrical length at a frequen'cy corresponding to the operating frequency of said transmitting arrangement as to comprise an impedance transformer for substantially lessening theloadprovided by saidsignal-translating channel 'on said transmitting arrangement during operating intervals of Wave-signal Vtransrnission.

16. AWave-signal receiver arrangement for operation at a predetermined frequency to tra-nslate received `Wave signals and adapted to share 'a common antenna system having a predetermined terminal impedance at said predetermined frequency with an arrangement for transmitting wave signals of a frequency which corresponds substantially to said predetermined frequency comprising, a signal-translating channel having an input circuit which presents to said antenna system during operating intervals of normal wave-signal reception a terminal impedance approximately equal, to said predetermined impedance and which tends to provide a substantial load on said transmitting arrangement during operating intervals of Wave-signal transmission, means including a rectier device exclusive of said signal-translating channel and responsive to said transmitted signals for deriving a control eiTect, means for utilizing said control effect to cause said input circuit to have a modified terminal impedance during operating intervals of Wave-signal transmission, and an adjustable transmission-line section having a characteristic impedance corresponding to said predetermined impedance for coupling said signal-translating channel to said antenna system with substantial impedance matching during intervals of wave-signal reception and having such an eiective electrical length at a frequency corresponding to the operating frequency of said transmitting arrangement as to comprise an impedance transformer for substantially lessening the load vprovided by said signal-translating channel 0n said transmitting arrangement during operating intervals `of Wave-signal transmission.

HAROLD A. WHEELER.

CES CITED The following references are of record in the file of this patent:

UNI'I'ED STATES PATENTS Number Name Date 1,872,398 Brown Aug. 16, 1932 2,101,549 Lamb Dec. 7, 1937 

